If you are dead set on a 1911, may I recommend a aluminum frame Commander size weapon.
Often considered a Expert's choice, the Combat Commander format is as good as the 1911 can get without sacrificing reliability. 10mm is a good caliber, allowing softball loads and full power loads. 45 ACP would be second choice.
On paper .357 Sig equals a .357 Mag in an Auto, though I have heard that itcan be unpleasant to shoot, expensive to feed, and life span is shorter.
3. Good trigger, good sights, good balance.